Bubbling plate for sliding nozzle

ABSTRACT

A bubbling plate for a sliding nozzle includes a plate body defining an inner hole therein and a gas-permeable ring installed inside the plate body to define part of the inner hole. The ring has a lower end surface formed with a stepped part, a convex part or a concave part; and the plate body has an upper surface in contact with the lower end surface with the upper surface formed with a stepped part, a concave part or a convex part capable of being opposed to and fittingly engaged with a corresponding part of the ring. The area in which the part of the ring is fittingly engaged with the corresponding part of the plate body has a length of 2 mm or more along a direction of a central axis of the inner hole, and mortar is interveningly provided in at least a longitudinally-extending joint part in the fitting engagement area.

TECHNICAL FIELD

The present invention relates to the structure of a so-called bubbling plate having a gas injection function and for a sliding nozzle used for continuous casting of steel.

BACKGROUND ART

In an upper plate of a sliding nozzle device, a so-called bubbling plate is frequently used in which a gas-permeable refractory member is installed to define at least a part of an inner hole of the bubbling plate, so as to inject gas into molten metal. This bubbling plate has a function of injecting inert gas such as argon gas into inner holes (nozzle holes) of various nozzles serving as a molten steel discharge path, for the purpose of preventing inclusions such as alumina from adhering onto the inner holes.

As such a bubbling plate, the below-mentioned Patent Document 1 discloses a gas injection device which comprises a bottom plate (plate body) defining an inner hole therein, and a gas injecting ring (tubular-shaped gas-permeable refractory member) installed inside the bottom plate to define a part of the inner hole. In this gas injection device, the gas injecting ring is provided with an iron cylindrical member on an outer peripheral surface thereof, and a lower part of the inner hole of the bottom plate (plate body) is defined by a reduced-diameter portion of the bottom plate, wherein the gas injecting ring is installed such that a bottom surface thereof is in contact with and locked to an upper surface of the reduced-diameter portion to define an upper part of the inner hole.

The below-mentioned Patent Document 2 discloses a gas injecting upper plate which comprises an upper plate refractory body (plate body) formed with an annular-shaped boss portion, and a gas channel (tubular-shaped gas-permeable refractory member) disposed inside the boss portion and formed with a plurality of gas introduction small holes.

CITATION LIST Patent Document

Patent Document 1: JP-U H06-041962

Parent Document 2: JP-A 2004-268106

SUMMARY OF INVENTION Technical Problem

Both the Parent Documents 1 and 2 disclose a structure in which a tubular-shaped gas-permeable refractory member, i.e., a gas-permeable, ring-shaped component (hereinafter also referred to as “ring”), is installed inside the plate body to define a part of the inner hole of the plate body, wherein a lower end (bottom) surface of the ring is in contact with an upper surface of the plate body (including a case where mortar intervenes therebetween) to allow the ring to be fixed.

However, in such a conventional ring installation structure, a trouble that molten steel intrudes into a gas pool provided between an outer periphery of the ring and the plate body (such a gas pool will hereinafter be referred to simply as “gas pool”) and solidifies, thereby causing stop of gas supply to the ring, can occur frequently.

A technical problem to be solved by the present invention is to provide a bubbling plate comprising a plate body defining an inner hole therein, and a ring installed inside the plate body to define a part of the inner hole, wherein it is capable of preventing intrusion of molten steel into a gas pool.

Solution to Technical Problem

The present invention provides a bubbling plate having features described in the following sections 1 to 7.

1. A bubbling plate for a sliding nozzle used for continuous casting of steel, wherein the bubbling plate comprises: a plate body defining an inner hole therein; and a gas-permeable, ring-shaped component (hereinafter referred to as “ring”) installed inside the plate body to define a part of the inner hole; wherein: the ring has a lower end surface formed with one of a stepped part, a convex part and a concave part; and the plate body has an upper surface in contact with the lower end surface of the ring, wherein the upper surface is formed with one of a stepped part, a concave part and a convex part each capable of being opposed to and fittingly engaged with a corresponding one of the stepped part, the convex part and the concave part of the ring; and wherein: an area in which one of the stepped part, the convex part and the concave part of the ring is fittingly engaged with a corresponding one of the stepped part, the concave part and the convex part of the plate body (said area will hereinafter be referred to as “fitting engagement area”) has a length of 2 mm or more along a direction of a central axis of the inner hole (said direction will hereinafter be referred to as “longitudinal direction”); and mortar is interveningly provided in at least a longitudinally-extending joint part in the fitting engagement area.

2. The bubbling plate described in the section 1, wherein the stepped part of the ring is formed such that a region of the lower end surface of the ring on the side of an outer periphery of the ring protrudes downwardly with respect to a region of the lower end surface of the ring on the side of the inner hole, and the stepped part of the plate body is formed such that a region of the upper surface of the plate body on the side of the inner hole protrudes upwardly with respect to a region of the upper surface of the plate body on the side of an outer periphery of the ring.

3. The bubbling plate described in the section 1 or 2, wherein a part or entirety of a longitudinally-extending surface in each of the stepped parts is parallel to the central axis of the inner hole.

4. The bubbling plate described in the section 1, wherein the fitting engagement area is formed between the convex part of the ring and the concave part of the plate body, wherein a part or entirety of a longitudinally-extending part of a fitting engagement surface located on the side of the inner hole in the fitting engagement area is parallel to the central axis of the inner hole.

5. The bubbling plate described in the section 1, wherein the fitting engagement area is formed between the concave part of the ring and the convex part of the plate body, wherein a part or entirety of a longitudinally-extending part of a fitting engagement surface located on the side of the outer periphery in the fitting engagement area is parallel to the central axis of the inner hole.

6. The bubbling plate described in any one of the sections 1 to 5, wherein the ring comprises a gas-permeable portion made of a porous refractory material.

7. The bubbling plate described in any one of the sections 1 to 5, wherein the ring comprises a gas-permeable portion composed of a refractory component having one or more through-holes.

Effect of Invention

The present invention can provide a bubbling plate comprising a plate body defining an inner hole therein and a ring installed inside the plate body to define a part of the inner hole, wherein it is capable of preventing intrusion of molten steel into a gas pool. This makes it possible to prevent deterioration in quality of steel due to outage of the gas injection function or occurrence of a negative influence on casting operation due to clogging of a molten steel passage (inner hole).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a relevant part of a bubbling plate according to one embodiment of the present invention.

FIG. 2 is a sectional view of a relevant part of a bubbling plate according to another embodiment of the present invention.

FIG. 3 is a sectional view of a relevant part of a bubbling plate according to yet another embodiment of the present invention.

FIG. 4 is an enlarged view of a fitting engagement area of the bubbling plate in FIG. 1 .

FIG. 5 illustrates an example of a conventional commonly-used bubbling plate.

DESCRIPTION OF EMBODIMENTS

As shown in FIG. 5 , a conventional commonly-used bubbling plate 1 comprises a plate body 2 defining an inner hole 2 d therein, and a ring 3 installed inside the plate body 2 to define a part of the inner hole 2 d, wherein a contact interface between a lower end (bottom) surface of the ring 3 and an upper surface of the plate body 2 (the contact interface will hereinafter be referred to as “joint surface”) is substantially planar with no irregularities.

From the result of observation of steel-intruded bubbling plates, the present inventors have found that the intrusion of molten steel into a gas pool 4 occurs mainly via the joint surface.

The major cause includes the inclination of the ring 3 when installed, variations in thickness of a joint, and the like, and the accuracy of the ring 3 and the plate body 2, and the like. Particularly in a structure in which the ring 3 and the plate body 2 are in linear contact with each other, due to relative movement or displacement therebetween, a gap is more likely to occur in a joint part therebetween, or molar in the joint part is likely to be partially broken, leading to disappearance of the mortar. Further, the gap caused by the linear contact between the ring 3 and the plate body 2 is more likely to connect to the gas poor 4 on the side of an outer periphery of the ring 3.

As a measure against the above major cause, the present invention provides a structure in which a ring 3 and a plate body 2 are not in linear contact with each other, i.e., a structure in which: the ring 3 has a lower end surface formed with one of a stepped part 3 a, a convex part 3 b and a concave part 3 c; and the plate body 2 has an upper surface in contact with the lower end surface of the ring 3, wherein the upper surface is formed with one of a stepped part 2 a, a concave part 2 b and a convex part 2 c each capable of being opposed to and fittingly engaged with a corresponding one of the stepped part 3 a, the convex part 3 b and the concave part 3 c of the ring 3; wherein the lower end surface of the ring 3 and the upper surface of the plate body 2 are fittingly engaged with each other by means of the pair of stepped parts or concave or convex parts, through a joint, as exemplified in FIGS. 1 to 3 .

Specifically, in a bubbling plate 1 illustrated in FIG. 1 , a stepped part 3 a of a ring 3 and a stepped part 2 a of a plate body 2 are fittingly engaged with each other to form a fitting engagement area A.

In a bubbling plate 1 illustrated in FIG. 2 , a convex part 3 b of a ring 3 and a concave part 2 b of a plate body 2 are fittingly engaged with each other to form a fitting engagement area A.

In a bubbling plate 1 illustrated in FIG. 3 , a concave part 3 c of a ring 3 and a convex part 2 c of a plate body 2 are fittingly engaged with each other to form a fitting engagement area A.

In FIGS. 1 to 3 and 5 , the reference sign 7 denotes a gas introduction passage for introducing gas to the gas poor 4.

In the present invention, the length of the fitting engagement area A along the longitudinal direction (hereinafter referred to as “fitting engagement length”) is set to 2 mm or more. Specifically, the present inventors have found that, in order to maintain a mechanical fixing between the ring 3 and the plate body 2 in the fitting engagement area A, i.e., to maintain a structure in which the ring 3 and the plate body 2 are butted against each other in an immobilized manner, a fitting engagement length of 2 mm or more is required.

Here, the fitting engagement length is a length L of a longitudinally-extending joint part in the fitting engagement area A, excluding the thickness of horizontally-extending joint parts 5 between the lower end surface of the ring 3 and the upper surface of the plate body 2, as shown in, e.g., FIG. 4 . In the case where the fitting engagement area A is composed of the pair of concave and convex parts as in FIGS. 2 and 3 , there are two longitudinally-extending joint parts on the side of the inner hole and on the side of the outer periphery, i.e., two fitting engagement lengths. In this case, either one of the two fitting engagement lengths may be set to 2 mm or more to obtain the intended effect of the present invention.

The upper limit of the fitting engagement length is not particularly limited. However, from a practical point of view, after ensuring a longitudinal length of a joint part between the outer periphery of the ring and the plate body (e.g., a length of about 5 to 10 mm from respective upper ends of the ring and the plate body) and a longitudinal length of the gas pool, it may be set to become equal to or less than a value (e.g., about 40 mm) obtained by subtracting the total longitudinal length of the joint part and the gas poor from a longitudinal length of the inner hole of the plate body.

In the present invention, mortar is interveningly provided in at least the longitudinally-extending joint part 6 in the fitting engagement area A (see FIG. 4 ). Specifically, in the bubbling plate 1 illustrated in FIG. 1 , mortar is interveningly provided in the longitudinally-extending joint part between the stepped part 3 a of the ring 3 and the stepped part 2 a of the plate body 2 in the fitting engagement area A. In the case where the fitting engagement area A is composed of the pair of concave and convex parts as in FIGS. 2 and 3 , there are two longitudinally-extending joint parts on the side of the inner hole and on the side of the outer periphery in the fitting engagement area A. In this case, mortar may be interveningly provided in either one of the two longitudinally-extending joint parts.

By interveningly providing mortar in the longitudinally-extending joint part in the fitting engagement area A in the above manner, a gap becomes less likely to occur at least in the longitudinally-extending joint part, even if the ring 3 is installed with a slight inclination with respect to the plate body 2.

Incidentally, in each of the bubbling plates 1 illustrated in FIGS. 1 to 3 , mortar is interveningly provided in the entire joint part in the fitting engagement area.

In the present invention, based on the above configuration, a contact interface between the ring 3 and the plate body 2 is non-linearly formed, and thus becomes less likely to be influenced by the afore-mentioned displacement or the like during installation of the ring 3, so that it becomes possible to prevent intrusion of molten steel into the gas pool 4 provided on the side of the outer periphery.

The present inventors have found that such intrusion is also caused by a thermal condition during casting (use), in addition to the aforementioned major cause.

Specifically, the plate body 2 is made of a refractory material which is denser and is mostly comprised of components having a higher thermal conductivity, as compared with the ring 3, and has a relatively large surface which comes into contact with molten steel during casting, so that relatively large thermal expansion occurs therein. On the other hand, the ring 3 which is continuously cooled by gas is maintained at a lower temperature than the plate body 2. Thus, even if the ring 3 has a similar thermal expansion property to that of the plate body 2, a thermal expansion amount of the ring 3 is less than that of the plate body 2

This can cause a situation where a gap occurs in the joint part, and molten steel intrudes into the gas pool 4.

As a measure against this cause, it is preferable that, in the fitting engagement area, the plate body 2 whose thermal expansion amount is greater than that of the ring 3 is disposed on the side of the inner hole, and the ring 3 whose thermal expansion amount is less than that of the plate body 2 is disposed on the side of the outer periphery. In this case, when the plate body 2 thermally expands, it presses the ring 3, and compresses the longitudinally-extending joint part therebetween, so that a gas becomes much less likely to occur.

More specifically, in the case where the pair of counterpart stepped parts are fittingly engaged with each other as in FIG. 1 , the stepped part 3 a of the ring 3 is formed such that a region of the lower end surface of the ring 3 on the side of the outer periphery protrudes downwardly with respect to a region of the lower end surface of the ring 3 on the side of the inner hole 2 d, and the stepped part 2 a of the plate body 2 is formed such that a region of the upper surface of the plate body 2 on the side of the inner hole 2 d protrudes upwardly with respect to a region of the upper surface of the plate body on the side of the outer periphery.

In the case where the convex part 3 b of the ring 3 and the concave part 2 b of the plate body 2 are fittingly engaged with each other as in FIG. 2 , or in the case where the concave part 3 c of the ring 3 and the convex part 2 c of the plate body 2 are fittingly engaged with each other as in FIG. 3 , an interface in which the plate body 2 exists on the side of the inner hole 2 d in a radial direction of the inner hole 2 d with respect to the ring 3 is certainly formed. Thus, when the plate body 2 thermally expands, it presses the ring 3, and compresses the longitudinally-extending joint part therebetween, so that a gas becomes much less likely to occur.

Preferably, a part or entirety of a longitudinally-extending surface in each of the stepped parts 3 a, 2 a is parallel to a central axis B of the inner hole 2 d. Further, in the case where he fitting engagement area A is formed between the convex part 3 b of the ring 3 and the concave part 2 b of the plate body 2 (see FIG. 2 ), it is preferable that a part or entirety of a longitudinally-extending part of a fitting engagement surface located on the side of the inner hole 2 d in the fitting engagement area A (see FIG. 2 ) is parallel to the central axis B of the inner hole 2 d. On the other hand, in the case where the fitting engagement area A is formed between the concave part 3 c of the ring 3 and the convex part 2 c of the plate body 2, it is preferable that a part or entirety of a longitudinally-extending part of a fitting engagement surface located on the side of the outer periphery in the fitting engagement area A is parallel to the central axis B of the inner hole 2 d.

By configuring the fitting engagement area in the above manner, it becomes possible to further enhance an action of the plate body 2 to press the ring 3 in a radially outward direction in the fitting engagement area, and thus further enhance an action of the plate body 2 to compress a joint in the fitting engagement area, thereby further strengthening sealing performance of the joint.

In the present invention, the ring 3 may comprise a gas-permeable portion which is made of a so-called porous refractory material whose refractory microstructure itself has a function of allowing gas to pass therethrough or discharging gas therethrough, or which is composed of a refractory component made of a so-called dense refractory material whose refractory microstructure itself has no function of allowing gas to pass therethrough or discharging gas therethrough, and formed with one or more through-holes each of which penetrates through the refractory microstructure to extend from the gas pool 4 on the side of the outer periphery of the ring 3 to an inner peripheral surface of the ring 3 defining a part of the inner bore 2 d.

LIST OF REFERENCE SIGNS

-   1: bubbling plate -   2: plate body -   2 a: stepped part -   2 b: concave part -   2 c: convex part -   2 d: inner hole -   3: ring -   3 a: stepped part -   3 b: convex part -   3 c: convex part -   4: gas pool -   5: horizontally-extending joint part between lower end surface of     ring and upper surface of plate body -   6: longitudinally-extending joint part in fitting engagement area -   7: gas introduction passage -   A: fitting engagement area -   B: central axis of inner hole (longitudinal direction) 

1. A bubbling plate for a sliding nozzle used for continuous casting of steel, comprising: a plate body defining an inner hole therein; and a gas-permeable, ring-shaped component (hereinafter referred to as “ring”) installed inside the plate body to define a part of the inner hole; wherein: the ring has a lower end surface formed with one of a stepped part, a convex part and a concave part; and the plate body has an upper surface in contact with the lower end surface of the ring, the upper surface being formed with one of a stepped part, a concave part and a convex part each capable of being opposed to and fittingly engaged with a corresponding one of the stepped part, the convex part and the concave part of the ring; and wherein: an area in which one of the stepped part, the convex part and the concave part of the ring is fittingly engaged with a corresponding one of the stepped part, the concave part and the convex part of the plate body (said area will hereinafter be referred to as “fitting engagement area”) has a length of 2 mm or more along a direction of a central axis of the inner hole (said direction will hereinafter be referred to as “longitudinal direction”); and mortar is interveningly provided in at least a longitudinally-extending joint part in the fitting engagement area.
 2. The bubbling plate as claimed in claim 1, wherein the stepped part of the ring is formed such that a region of the lower end surface of the ring on the side of an outer periphery of the ring protrudes downwardly with respect to a region of the lower end surface of the ring on the side of the inner hole, and the stepped part of the plate body is formed such that a region of the upper surface of the plate body on the side of the inner hole protrudes upwardly with respect to a region of the upper surface of the plate body on the side of the outer periphery.
 3. The bubbling plate as claimed in claim 1, wherein a part or entirety of a longitudinally-extending surface in each of the stepped parts is parallel to the central axis of the inner hole.
 4. The bubbling plate as claimed in claim 1, wherein the fitting engagement area is formed between the convex part of the ring and the concave part of the plate body, wherein a part or entirety of a longitudinally-extending part of a fitting engagement surface located on the side of the inner hole in the fitting engagement area is parallel to the central axis of the inner hole.
 5. The bubbling plate as claimed in claim 1, wherein the fitting engagement area is formed between the concave part of the ring and the convex part of the plate body, wherein a part or entirety of a longitudinally-extending part of a fitting engagement surface located on the side of the outer periphery in the fitting engagement area is parallel to the central axis of the inner hole.
 6. The bubbling plate as claimed in claim 1, wherein the ring comprises a gas-permeable portion made of a porous refractory material.
 7. The bubbling plate as claimed in claim 1, wherein the ring comprises a gas-permeable portion composed of a refractory component having one or more through-holes. 